Is playing video games that include characters claiming to possess divine powers, or that include bowing to idols to gain advantages, considered disbelief (kufr), even if the player does not actually bow?

It is not permissible to play games that include anything contrary to Islamic creed. The player of such games commits a sin, even if it does not amount to disbelief. The whispers (waswasa) related to disbelief are caused by giving in to them, and their cure is to turn away from them and pay them no mind, after seeking Allah's help.